[cleanup] Move methods to V8_DEPRECATED

Updates ObjectTemplate::NewInstance and FunctionTemplate::GetFunction
from V8_DEPRECATED_SOON to V8_DEPRECATED, now that they're unused in
chrome.

Bug: v8:7294, v8:7295, v8:8238
Change-Id: Ic7cb2c410ff812f73cfd108551f2a1a20722df07
Reviewed-on: https://chromium-review.googlesource.com/c/1344151Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57657}

include/v8.h

@@ -5738,7 +5738,7 @@ class V8_EXPORT FunctionTemplate : public Template {
       SideEffectType side_effect_type = SideEffectType::kHasSideEffect);
 
   /** Returns the unique function instance in the current execution context.*/
-  V8_DEPRECATE_SOON("Use maybe version", Local<Function> GetFunction());
+  V8_DEPRECATED("Use maybe version", Local<Function> GetFunction());
   V8_WARN_UNUSED_RESULT MaybeLocal<Function> GetFunction(
       Local<Context> context);
 
@@ -6035,7 +6035,7 @@ class V8_EXPORT ObjectTemplate : public Template {
                                                  size_t index);
 
   /** Creates a new instance of this template.*/
-  V8_DEPRECATE_SOON("Use maybe version", Local<Object> NewInstance());
+  V8_DEPRECATED("Use maybe version", Local<Object> NewInstance());
   V8_WARN_UNUSED_RESULT MaybeLocal<Object> NewInstance(Local<Context> context);
 
   /**